* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

@media all and (min-width:300px) {
    html {
        font-size: calc(100vw / 5);
    }
    .main {
        width: 100vw;
    }
    .top-pic {
        height: 2rem;
    }
}

@media all and (min-width:750px) {
    html {
        font-size: calc(100vw / 7.5);
    }
    .main {
        width: 100vw;
    }
    .top-pic {
        height: 2.7rem;
    }
}

@media all and (min-width:1000px) {
    html {
        /* 1500px设计稿  1rem  ==>100px*/
        font-size: calc(100vw / 15);
    }
    .main {
        width: 9rem;
    }
    .top-pic {
        height: 4.5rem;
    }
}

@media all and (min-width:1600px) {
    html {
        font-size: calc(100vw / 20);
    }
    .main {
        width: 9rem;
    }
}

body {
    font-size: 0.16rem;
}